Concrete Bag Calculator — Fast & Simple
Enter your dimensions (slab or post holes) or a total volume and instantly see how many 40, 50, 60, and 80 lb bags you need. The tool also shows total weight, estimated mixing water, and optional cost. Perfect for patios, sheds, fence posts, and small pours.
Default Yields (per bag)
- 40 lb ≈ 0.30 ft³
- 50 lb ≈ 0.375 ft³
- 60 lb ≈ 0.45 ft³
- 80 lb ≈ 0.60 ft³
Bag yields vary by product and mix design. If your bag label lists a different yield, use that for the most accurate estimate.
Quick Answers
- How many 80 lb bags in a yard? ≈ 45 bags
- How many 60 lb bags in a yard? ≈ 60 bags
- How much water per 80 lb bag? ~3–4 quarts (follow product label)
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FAQs
How many 80 lb bags of concrete are in a cubic yard?
A cubic yard is 27 cubic feet. With a typical 80 lb bag yield of about 0.60 ft³, you’ll need about 45 bags (27 ÷ 0.60 = 45).
How much water do I need per bag?
Water varies by mix. Many 80 lb bags use roughly 3–4 quarts per bag, but always follow the manufacturer’s label instructions.
Should I order extra for waste?
Yes. A 5–10% waste factor is common for small pours to account for spillage, uneven edges, and mixing losses.
When does ready-mix make more sense than bags?
For larger pours (often around 2+ yd³), ready-mix can be faster and sometimes cheaper once you factor in mixing time, labor, and consistency.
Can I use this calculator for footings and post holes?
Yes. Use the Post Holes/Sonotubes tab for cylindrical holes. For footings, use the Slab/Pad tab with footing dimensions or the By Volume tab.
Accuracy & Review
Reviewed by: Maria Ramirez, PE
Maria is a licensed Professional Engineer (PE) with experience reviewing residential and light commercial concrete quantity takeoffs. She reviewed the formulas, unit conversions, rounding rules, and default yield assumptions used in this calculator.
Last updated:
See: Methodology · Data Sources · Review Board
Important Estimate Disclaimer
Results are provided for general planning purposes only and do not constitute engineering or structural design advice. Actual material quantities may vary based on site conditions, reinforcement design, slab thickness, and local building code requirements.
See our Methodology and Data Sources for calculation details.
Subgrade preparation, load-bearing requirements, expansion joints, and curing conditions can significantly affect final concrete volume. Structural or frost-exposed installations should be reviewed by a qualified professional.